Gripper release mechanism for sheet handling machines



Dec. 25, 1951 H. BOBST 2,579,540

GRIPPER RELEASE MECHANISM FOR SHEET HANDLING MACHINES Filed April 11,1946 Inventor HEM?! Baasr fldtorneys Patented Dec. 25, 1951 GRIPPERRELEASE MECHANISM FOR SHEET HANDLING MACHINES Henri Bobst, Lausanne,Switzerland Application April 11, 1946, Serial No. 661,302 r InSwitzerland April 12, 1945 r 1 The present invention relates to releasemechanism for the grippers of machines for working sheets of paper,cardboard or the like.

In such machines, the said sheets are transported by gripper bars placedbetween two endlesschains disposed in parallel relationship, and thebars stop successively at a registering station, where the associatedgrippers seize the sheets one by one, at a working station and at adeliverystation where the grippers are opened thereby stacking thesheets.

A special mechanism is provided at the delivery station for opening thegrippers when desired and functioning normally as long as the sheetsarrive and leave the bars in. good order, one by one.

Since normal operation can easily involve an accident causing a stoppagelikely to damage certain parts of the mechanism or even twistthe bars,it is the object-of the present invention to provide a mechanisminsuring the proper delivery and obviating any accident of this kind bystopping the machine in good time.

To this end, the parts which open the grippers oscillate upon an axlerotating in bearing supported by pivoting elements, and held by springdetent in a normal position from which they depart only when the openingmechanism is actuated by an exceptional outside directive force, thepivoting of the elements under consideration having the result ofstopping the machine and with it the forward movement of the bars.

In the accompanying drawing which shows an embodiment of the mechanismsaccording to the present invention, given by way of example:

Figure 1 is avertical section view taken along the longitudinal axis ofthe machine, that is according to a median plane situated between thetwo chains;

Figures 2 and 8 are sections of two couplings producing spring detent;and

Figure 4 shows the mechanism in a perspective view.

On a fixed axle I two chain-wheels are mounted for free rotation one ofwhich is shown in dot and dash line and marked 2. The position of thechain carried by this wheel is shown in the same way and marked 3. Thechains convey gripper bars 4, of which one is shown in transversesection, with a blade spring 5 forming a gripper and a plunger 6 whichrising, may cause the opening of this gripper.

Each bar has as many springs and plungers as it has grippers and, in thereception position 9 Claims. (Cl. 271-79) in which it is shown, thereare provided as many abutment screws 1 disposed opposite the plungers tocooperate therewith.

Each screw is supported by an arm 8 of a common rotative axle 9oscillated by a lever [0, in turn actuated :by the links I l and I2,through bell-crank lever I3 pivoted at I4.

A momentary displacement of the links H and I2 in the direction of thearrow l5 causes the axle 9 to oscillate anti-clockwise in relation tothe drawing, and the screws 1 open the grippers 5 by means of theplungers 6, allowing the sheet transported by the bar 4 to fall in thedirection of the arrow It on the stack H. The displacement of link I2 ismost conveniently caused and timed in the manner described in copendingapplication Serial Number 663,396, filed April 19, 1946.

The perspective view of Figure 4 shows clearly the main part of theabove mentioned elements.

At each end, the axle 9 is jeurnalled in bearings each forming a part ofan oscillatory ele ment of which the drawing shows one in the shape of atriangularly shaped plate 18, fixed to the frame IQ of the machine byfixed pivot 28. This plate is is however held against rotation by a pin2 I, of which the head co-operates, under the action of a spring 22 (seeFig. 2) with a conical hole 23 of the wall of the frame l9. It may besaid that this coupling maintains the plate It by spring detent in itsnormal position, as shown.

This detent is in particular sufficient to prevent the reaction, arisingfrom the opening op eration of the grippers, from displacing the plate18. This reaction is anyway practically negligible, because upon openingof the grippers, the pressure exerted by the link I I and the resistanceofiered by the opening efiort are practically parallel to each other,having a resultant passing very near the centre of the pivot 20,therefore not able to impart a torque to the plate [8 sumcient todisengage it.

If, on the contrary, such members as the abutment screws 1, the arms 8or the axle 9 undergo an exceptionally directed strain, for exampleowing to pressure arising from stoppage produced by the transport ofseveral sheets, of a crumpled sheet, etc. in the direction ofdisplacement of the bar 4, it is obvious that these members will tend tobe displaced, which will allow the rotation of the plate l8 about thepivot 29, to position It. In this case the pin 21 leaves the conicalhole 23.

However, by means of its surface 24 the plate l8 then causes the campiece to oscillate round its fixed point 26, so that its abutment 21actuates the switch 28 which, in turn, stops the machine. The drawingshows the switch closed by abutment 21, but the particular wiring mightjust as well call for opening of the switch in a like manner W a 1 Themechanism shown therefore fulfills the condition proposed, that is toobviate all accidents arising from an accidental stoppage: not only doesit stop the machine, but by the displacement of members i, 8 and 9responsive to the strain of stoppage, it creates adiscontinuity in thedelivery sufficient for the passage of at least a part of the disturbingelements. w I

Below the mechanism so far described, the example shown includes aregistering member; the purpose of which is to correct the position ofthe sheets as they fall on the stack II. This membercomprises an axle29, carrying several arms' s uch as so. A link 31 imparts thereto anoscillatory movement by means of a lever 32. This movement brings thefingers 39 alternatively to the position where they lean against theupper. rear edge of the stack I1, thus constraining the last sheetdeposited to alignitselfcorrectly. The extreme position 3| and 32'occupied by the link, and the lever 32 correspond to 7 position 30 ofarmsBG at each oscillation.

Thedetail of Figure 3 shows finally how the lever 3 2 is coupledto theaxle 29 by means of Screw 33, of a pressure spring 3 1 and of a ball 35.penetrating into a' depres'sion of the said axle.

coupling is therefore automatically disengageable and acts as a safetyrelease mechmm to allow arms 39 to free themselves if a stoppage of anykind were to causea resistance or an abnormal strain in the direction ofrotation as by the occurrence of jammed or 'buckled sheets at the sheetreleasing station. a

The axle 23, once liberated from the lever 32, is thenireeto continue torotate under the force of the buckled or jammed sheets and carries withit the cam 36 on which leans an abutment screw ofthe cam piece 25. Thislatter is rotated in thesame direction as by cam 24 to causedispl'acementof the plate l8, i. e. so that its abutment 2'! acts on theswitch 28 and stops the machine.

This arrangement constitutes an additional guarantee against allaccidents due to a stoppage at, any, point of the station where thesheets are deposited.

What'I claim is:

1. In a machine for working sheets of paper; the combination of sheetconveying bars movable through said machine, gripping means on each ofsaid bars for holding a sheet to the latter, and means at a sheetreleasing station operative to release said gripping meansand comprisingan oscillatable axle carrying releasing bumpers for releasing engagementwith said gripping means, means for oscillating said axle to effectengagement and disengagement between said releasing bumpers and saidgripping means, swingable supports for the opposite ends of said axlepivoted for swinging motion about an axis displaced radially from theaxis of turning of said axle so that thelatter may move bodily betweenan op- 'erative position in which said releasing bumpers at said stationoperative to release said gripping means and comprising an oscillatableaxle carrying radially extending bumpers for releasing engagement withsaid gripping means, at least one radial arm extending from said axleactuat ing rneansconnected to said armand applying an intermittent forceto the latter for oscillating said axle to eiTect engagement anddisengagement :between said bumpers and said gripping means onsuccessive bars atsaid station, swingable supports forpth'e oppositeends of said axle pivotally mounted for swinging motion about an 7 axisdisplaced radially from the axis of turning of said axle so that thelatter may move bodily between a-n operative position in which said releasing bumpers are engageable with said grip- The cam piece 25 isfinally connected with a V rod 31; the end of which projects from thecasing 38 of the machine to form a push knob; making it possible to stopthe machine at will. Pressure on this rod causes the cam piece 25 tooscillate in the direction where it acts on the switch 28.

In Figure l of the drawing is also shown,- how orie'sr more arms 39 maybe disposed on axle I, each ending in a ro1ler 40 serving as a rest forthe -iipfier bars momentarily stopped at the position shown. Assumingthat such bars are relatively long, that they must be light and inconsequence as small as possible in section, so that the openingpressure of the grippers subjects them to a transversalstrain which isincreased if stoppage actuates theabove mechanism', it is important tosupportthem at one or more points. This support is. provided by roller40 resting on the axle I, the section of which is not limited by takingweight 'or obstruction into account.

ping means and an inoperative position in which said releasing bumpersare remote from said gripping means in all oscillated. dispositions ofsaid axle, the swinging axis of said supports being arranged so thatsaid intermittent force and the normalreaction force of said grippingmeans againstsaid bumpers provide substan tially equal and oppositelydirected turning moments about said swinging axis; and yieldable meansacting on said supports for maintaining said axle in said operativeposition so that the occurrence of an excessive reactionforce'betwe'e'nsaid gripping means and said bumpers imposes a turning moment on saidsupports to overcome the holding force of said yieldable means and toswing said supports for disposing said axle in said inoperative positionof the latter.

3. In a machine for working sheets of paper; the combination as setforth in claim 2, wherein said supports are mounted on adjacent framemembers, and wherein said yieldable means in} cludes a retaining memberaxially slid'abl'e in at least one of said supports, spring meansaxially U urging said retaining member against the face of the adjacentframe member. and a depres? sion in said face ofthe adjacent framemember located to receive aid retaining member when said axle is in saidoperative position thereof.

.. 4 in sma k n f r warms hei fi lie the oiirbination i. asset forth inclaim 2, rurtnei' including a cam-shaped surface on at least one of saidswingable supports., electrically driven operating means for saidmachine including circuit controlling switch means, and switch actuatingmeans engaged by said cam-shaped surface and operative to dispose saidswitch means in a circuit open condition when said supports swing withsaid axle to said inoperative position of the latter.

5. In a machine for working sheets of paper; the combination as setforth in claim 2, further including a pair of parallel chains carryingthe opposite ends of said sheet conveying bars, sprocket wheelssupporting said pair of chains in the area of said sheet releasingstation, a common shaft for said sprocket wheels, at least one radial.arm extending from said shaft and having a roller on its free end tosupport the successive.

and meansfor oscillating said shaft including a reciprocated link, anactuating radial arm turnable on said shaft and connected to saidreciprocated link, and yieldable means normally coupling said actuatingarm to said oscillatable 6 M switch means, and switch actuating meansengaged by said cam member and operative to dispose said switch means ina circuit open condition when said oscillatable shaft is displaced bythe jammed or buckled sheets through an angle greater than the extent ofthe normal oscillation of said shaft as such normal oscillation isinduced by said reciprocated link.

t. In a machine for working sheets of paper} the combination as setforth in claim 7, wherein said switch actuating means includes apivotally mounted switch actuating plate and a first follower on saidplate engaging the cam surface of said cam member, and wherein said camsurface of the cam member is formed with a portion formed with all partsthereof equidistant from the axis of said shaft and normally engagingsaid first follower and with a radially raised portion engaging saidfirst follower when said shaft is displaced through said greater angle.

9. In a machine for working sheets of paper; the combination as setforth in claim 8, further including a cam-shaped surface on at least oneshaft to provide a normal oscillation of said shaft. 1

7. In a machine for working sheets of paper;

the combination as set forth in claim 6, further including means forstopping operation of the comprising a cam member fixed on saidoscillatable shaft, electrically driven operating means? for saidmachine including circuit controlling of said swingable supports, and asecond follower REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,079,218 Curtis Nov. 18, 19131,826,463 Gibson Oct. 6, 1931 2,138,407

Huck Nov. 219, 1938

